Check out example codes for "ios sms css". It will help you in understanding the concepts better.

Code Example 1

<section>
    <div class="from-me">
      <p>Hey there! What's up?</p>
    </div>
  <div class="clear"></div>
    <div class="from-them">
      <p>Checking out iOS7 you know..</p>
    </div>
  <div class="clear"></div>
    <div class="from-me">
      <p>Check out this bubble!</p>
    </div>
  <div class="clear"></div>
    <div class="from-them">
      <p>It's pretty cool!</p>
    </div>
  <div class="clear"></div>
    <div class="from-me">
      <p>Yeah it's pure CSS & HTML</p>
    </div>
  <div class="clear"></div>
    <div class="from-them">
      <p>Wow that's impressive. But what's even more impressive is that this bubble is really high.</p>
    </div>
  </section>

Code Example 2

body {
  font-family: "Helvetica Neue";
  font-size: 20px;
  font-weight: normal;
}

section {
  max-width: 450px;
  margin: 50px auto;
}
section div {
  max-width: 255px;
  word-wrap: break-word;
  margin-bottom: 20px;
  line-height: 24px;
}

.clear {
  clear: both;
}

.from-me {
  position: relative;
  padding: 10px 20px;
  color: white;
  background: #0B93F6;
  border-radius: 25px;
  float: right;
}
.from-me:before {
  content: "";
  position: absolute;
  z-index: -1;
  bottom: -2px;
  right: -7px;
  height: 20px;
  border-right: 20px solid #0B93F6;
  border-bottom-left-radius: 16px 14px;
  -webkit-transform: translate(0, -2px);
}
.from-me:after {
  content: "";
  position: absolute;
  z-index: 1;
  bottom: -2px;
  right: -56px;
  width: 26px;
  height: 20px;
  background: white;
  border-bottom-left-radius: 10px;
  -webkit-transform: translate(-30px, -2px);
}

.from-them {
  position: relative;
  padding: 10px 20px;
  background: #E5E5EA;
  border-radius: 25px;
  color: black;
  float: left;
}
.from-them:before {
  content: "";
  position: absolute;
  z-index: 2;
  bottom: -2px;
  left: -7px;
  height: 20px;
  border-left: 20px solid #E5E5EA;
  border-bottom-right-radius: 16px 14px;
  -webkit-transform: translate(0, -2px);
}
.from-them:after {
  content: "";
  position: absolute;
  z-index: 3;
  bottom: -2px;
  left: 4px;
  width: 26px;
  height: 20px;
  background: white;
  border-bottom-right-radius: 10px;
  -webkit-transform: translate(-30px, -2px);
}

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